Conventionally, an accumulator which includes a metal bellows is used for discharging a large amount of energy in a short time and reliving pressure fluctuations. In such an accumulator, in order to prevent the metal bellows from colliding with a pressure vessel when the metal bellows vibrates due to vibrations from the outside, a sliding ring which also has a bearing function is provided at the tip of the metal bellows. Such techniques will be described with reference to FIG. 6 and FIG. 7. Each of FIGS. 6 and 7 is a schematic cross-sectional view of an accumulator according to a conventional embodiment, and FIG. 6 shows a state in which the metal bellows is contracted while FIG. 7 shows a state in which the metal bellows is expanded.
An accumulator 500 according to the conventional embodiment includes a pressure vessel 600, a partition unit 700 which is provided in the pressure vessel 600 and partitions the pressure vessel 600 into a fluid chamber (L) in which a working fluid flows and a gas chamber (G) in which gas is sealed, and a stay 800 which is disposed in the partition unit 700. The pressure vessel 600 is constituted by a bottomed tubular pressure vessel main body 610, and a port formation member 620 which is provided so as to cover an opening portion of the pressure vessel main body 610 and has a port 621. The stay 800 is constituted by a bottomed tubular member which opens on the side of the port 621 and has an opening end portion fixed to the port formation member 620. A through hole 810 is provided at the bottom of the stay 800.
The partition unit 700 includes a tubular metal bellows 710 which has one end side fixed to the port formation member 620, a bellows cap 720 which is fixed to the other end side of the metal bellows 710, and a seal member 730 which is fixed to the bellows cap 720. The metal bellows 710 is configured so as to expand and contract according to pressure in the fluid chamber (L) and pressure in the gas chamber (G). In addition, a sliding ring 740 which also has the bearing function is provided on the outer periphery of the bellows cap 720. The outer peripheral surface of the sliding ring 740 is configured so as to be slidable relative to the inner peripheral surface of the pressure vessel main body 610. This enables the metal bellows 710 to expand and contract smoothly, and the vibration of the metal bellows 710 to be suppressed.
However, depending on various conditions such as the length, liquid storage amount, and magnitude and frequency of the vibration of the metal bellows 710, there is a possibility that the part of the metal bellows 710 in the vicinity of the middle thereof collides with the inner peripheral surface of the pressure vessel main body 610. That is, a clearance is provided between the outer peripheral surface of the sliding ring 740 and the inner peripheral surface of the pressure vessel main body 610. Accordingly, there are cases where the bellows cap 720 tilts when the metal bellows 710 is expanded. Thus, when the bellows cap 720 tilts, there is a possibility that the metal bellows 710 is deformed so as to tilt and the part of the metal bellows 710 in vicinity of the middle thereof collides with the inner peripheral surface of the pressure vessel main body 610 (see FIG. 7). This may cause the metal bellows 710 to be plastically deformed or damaged.